Heat is measured in either British Thermal Units (BTU) or Kilowatts (KW). The heat load depends on a number of factors, by taking into account those that apply in your circumstances and adding them together a reasonably accurate measure of the total heat can be calculated*.

Factors include: The floor area of the room The size and position of windows, and whether they have blinds or shades The number of room occupants (if any)The heat generated by equipment The heat generated by lighting Window Size and Position If, as is quite common, your Server Room has no windows, you can ignore this part of the calculation.